Gallium alkyls are the most practically used gallium precursors in the semiconductor industry. Among these, the most popular precursors for MOCVD/ MOVPE of Ga-containing layers is trimethylgallium Ga(CH3)3 (GaMe3) and triethylgallium Ga(C2H5)3 (GaEt3), f.e. of GaN (in combination with ammonia) [[i], [ii], [iii], [iv], [v], [vi], [vii], [viii]] as well as GaAs-based layers []. The advantage of GaMe3 is that it is a liquid precursor with high vapour pressure.
[i] J.I.Pankove, J.E.Berkeyheiser, H.P.Maruska, J.Wittke, J.Solid StateCommun., 1970, 8, 1051.
[ii] W.Seifert, A. Tempel, Phys. Status Solidi A, 1974, 23, K39.
[iii] R.Fremunt, P.Cerny, J.Kohout, V. Rosicka, A.Burger, Cryst.Res.Technol., 1981, 16, p.1257
[iv] K.Haniwae,S.Itoh, H.Amano, K. Itoh, K.Hiramatsu, I.Akasaki, J.Cryst.Growth,1990,99,381.
[v] R. Madar, G. Jacob, J. Hallais, R. Fruhart, J. Cryst. Growth, 1975, 31, 197
[vi] J.C. Knights, R.A. Lujan, J. Appl. Phys., 1984, 56, p.2367
[vii] M. Hashimoto, H. Amano, N. Sawaki, I. Aksasoki, J. Cryst. Growth, 1984, 68, p.163
[viii] M.A.Khan, R.A.Skogman, R.G.Schulze, M.Gershenzon, Appl. Phys. Lett., 1983, 42, 430
Trimethylgallium GaMe3
Trimethylgallium GaMe3 properties
GaMe3 is colorless liquid at RT (M = 114.83), very moisture sensitive and pyrophoric, mp. -15.8°C, bp. 55.7°C/760Torr[4] d = 1.151 g/mL (20°C), desnity 1.132 g/mL (25 °C) (other data 1.10 (RT))
It has high vapor pressure: logP(Torr) = 8.07-1703/T(K) logP(Torr) = 8.495-1825/T(K)
Vapor pressure (Torr): 22.0/-20°C, 29.7/-15°C, 39.7/-10°C, 52.4/-5°C, 68.5/0°C (64/0°C?[1], 64.5 Torr/0°C[Epichem, 3]), 88.6/5°C, 113.7/10°C, 144.6/15°C, 182.3/20°C, 228.2/25°C, 283.5/30°C
Decomposition mechanism
The decomposition of GaMe3 during low pressure MOCVD occurs by radical mechanism, producing monomethylgallium and two methyl radicals. The first methyl radical is formed via a homogeneous reaction above 500°C (bond energy 64.6 kcal/mol by molecular beam mass pectrometry, activation energy for radical removal 59.5 kcal/mol), while the second is liberated only >550°C (bond energy 52.6 kcal/mol, activation energy for radical removal 35.4 kcal/mol). The third Ga-Me bond (bond energy 54.1 kcal/mol) did not break under toluene flow conditions, but a solid (GaCH3)n polymer was formed instead. [2, [i]]. Ab initio molecular orbital calculations suggest the pyrolysis rate to be limited by homolysis of the first Ga-CH3 bond, with a calculated rate constant log10(k) = 16.33-(62.2/2.303RT) [[ii]].
A theoretical “best estimate” of Ga-Me bond energy of ΔH289K = 327.2 kJ/mol was calculated by quantummechanical calculations based on variational transition state theory This value is higher than experimentally determined energy of activation for the first homolytic Ga−C bond fission of GaMe3 (Ea = 249 kJ/mol), measured by Jacko and Price in a hot-wall tube reactor, suggesting experimental value is affected by surface catalytic effects. The preexponential factor A = 3.13 × 1016 1/s is an order of magnitude larger than the experimental results because of a larger release of entropy at the transition state as compared to that of the unknown surface catalyzed mechanism.[[iii]]
In the atmospheric pressure MOCVD, the pyrolysis reaction was found to be faster in H2 ambient compared to N2 [[iv]]. The exclusion of effects of hydrodynamical difference of carrier gases was achieved by showing that pyrolysis rate was increasing from He (similar to hydrogen hydrodynamically) to D2 and even higher with H2. The main pyrolysis product in H2 is methane (with small amounts of ethane and higher hydrocarbons), while in D2 the major product is CH3D with some C2H6, CH4 and CH2D2 formed as well. These data indicate hydrogenolysis being an important step in this reaction, with methyl radical being attacked by H2 (D2) molecule from ambient. Hydrogen (or D) radicals are abstracting methyl radicals from GaMe3, forming CH3D, CH3Ga and new methyl radicals participating in further chain reaction. Methyl radicals can also recombine forming small amounts of C2H6. [[v], [vi]]
The experiments of alternately adding to the GaMe3/H2 mixture of InMe3 (a low-temperature source of Me radicals) and 1,4-cyclohexadiene (an effective Me radical scavenger), showed no effect to the pyrolysis rate of GaMe3, proving that CH3 attack of GaMe3 is not a significant pyrolysis mechanism. [2]
In summarising the above data, the following mechanism of pyrolysis of GaMe3 in H2 at atmospheric pressure was proposed [2]:
(CH3)3Ga → CH3· + (CH3)2Ga·
{ CH3· + D2 → CH3D + D·
D· + (CH3)3Ga → CH3D + CH3Ga + CH3· } n
2 CH3· → C2H6 (chain termination)
[i] Q. Chen, P.D. Dapkus, J. Electrochem. Soc., 1991, 138, p.2821
[ii] S. Oikawa, M. Tsuda, M. Morishita, M. Mashita, Y. Kuniya, J. Cryst. Growth, 1988, 91, 471.
[iii] R. Schmid, D. Basting, J. Phys. Chem. A, 2005, 109 (11), pp 2623–2630
[iv] M. Yoshida, H. Watanabe, F. Uesugi, J. Electrochem Soc., 1985, 132, p677.
[v] C.A. Larsen, N.I. Buchan, G.B. Stringfellow, Appl.Phys. Lett, 1988, vol.52, p.480
[vi] C.A. Larsen, N.I. Buchan, S.H.Li, G.B. Stringfellow, J. Cryst. Growth, 1990, vol.102, p103
GaMe3 reaction with NH3 (transformation to GaN) mechanisms
Trimethylgallium GaMe3 (TMGa, Ga(CH3)3) in combination with NH3 is a standard precursor on the industrial scale for the CVD/ MOVPE of thin films of GaN [f.e. AIXTRON] [[i]].
The gas-phase thermal decomposition of GaMe3 in the presence of NH3 is well understood. The 2 main decomposition pathways during growth of GaN layers are described in [[ii]] (see Figure):
G1) radical decomposition pathway: breakdown of GaMe3 to dimethyl-gallium radical ∙GaMe2 with the subsequent loss of a methyl radical Me∙ producing monomethylgallium, which reacts with
G2) ammonia adduct formation/ molecular decomposition pathway: formation of GaMe3:NH3 adduct , which decomposes to dimethylgallium amide GaMe2-NH2 (with loss of CH4 molecule) and trimerises [GaMe2-NH2 ]3; the trimer loses CH4 molecules leaving GaN layer on the surface.
[i] www.aixtron.com
[ii] Rinku P. Parikh, Raymond A. Adomaitis, Journal of Crystal Growth 286 (2006) 259–278,An overview of gallium nitride growth chemistry and its effect on reactor design: Application to a planetary radial-flow CVD system
Surface chemistry of GaMe3 (ALE/ALD applications)
Surface chemistry of GaMe3 (as compared to Et2GaCl) on GaAs(100) surface was investigated in order to determine growth mechanisms of atomic layer epitaxy (ALE) of GaAs. During Ga deposition the reaction pathway of GaMe3 changes such that there is significant GaMe emission at high Ga coverages. An examination of the Ga coverage dependence reveals that this stoichiometry dependent GaMe desorption can lead to self‐limiting Ga deposition which is a prerequisite for ALE; numerical simulation of the reaction was in agreement with low‐pressure ALE growth data. For comparison, Et2GaCl was found to deposit GaCl on the GaAs surfaces, with residence time decreasing rapidly with increasing Ga coverage.[433]
GaMe3 for GaN MOCVD
Trimethylgallium is one of the main Ga precursors for the preparation of the GaN thin films by MOVPE.An overview of gallium nitride growth chemistry and its effect on reactor design was described by Parikh and Adomaitis in [[i]]:Formation of adducts between GaMe3 and ammonia was investigated in [[ii]] (details see AlMe3-NH3 adducts section)
[i] Rinku P. Parikh and Raymond A. Adomaitis , Journal of Crystal Growth, Volume 286, Issue 2, 15 January 2006, Pages 259-278.
[ii] G.T. Wang, J. R. Creighton, J. Phys. Chem. A, 2006, 110 (3), pp 1094–1099
GaMe3 for GaAs MOCVD
[i] P. Zanella, G. Rossetto, N. Brianese, F. Ossola, M. Porchia, J. O. Williams, Chem. Mater., 1991, 3 (2), pp 225–242 “Organometallic precursors in the growth of epitaxial thin films of III-V semiconductors by metal-organic chemical vapor deposition (MOCVD)”
[ii] A. G. Salinger, J. N. Shadid, S. A. Hutchinson, G.L. Hennigan, K.D. Devine, H. K. Moffat, J. Cryst. Growth, 1999, Vol.203, Iss 4, p.516-533
[iii] S. Schwetlick and W. Seifert, R. Pickenhain and R. Schwabe, Journal of Crystal Growth, Volume 96, Issue 2, June 1989, Pages 378-382, “Reduced EL2 concentration in MOCVD GaAs by addition of NH3 during growth”
GaMe3 for InGaAs, InGaAsP MOCVD
Trimethylgallium is widely applied as Ga precursor for the growth of InGaAs and InGaAsP thin films, both in industrial applications and research [[i]]
[i] R. H. Moss, Journal of Crystal Growth, Volume 68, Issue 1, 1 September 1984, Pages 78-87 , “Adducts in the growth of III–V compounds”
GaMe3 for AlGaAs MOCVD
GaMe3 is the most popular precursor for the growth of AlGaAs layers by MOCVD/ MOVPE, both in industry and research.
Thermodynamical aspects (including stability of the gasphase intermediates like GaMe and GaH2) during the growth of AlGaAs layers by MOCVD was presented in [[i]]
[i] M. Tirtowidjojo, R. Pollard, J. Cryst. Growth, Vol 77, Iss 1-3, Sep 1986, Pages 200-209, “ Equilibrium gas phase species for MOCVD of AlxGa1-xAs”
GaMe3 for Ga2O3 MOCVD
Trimethylgallium GaMe3 (TMGa), together with oxygen (O2) as an oxidant, have been applied for the MOCVD growth of Ga2O3 films on Si(100) substrates at 500–600°C growth temperature. Films were amorphous with very small crystallites and smooth; surface roughness increased with increasing growth temperature [450]
GaMe3 for Ga2O3 ALD
Trimethylgallium GaMe3 has been successfully as high-temperature ALD precursor depositing low-contaminant level Ga2O3 layers at good growth rate [[i]]
[i] Goldstein, David Nathan, “Surface chemistry of the atomic layer deposition of metals and group III oxides”, Thesis (Ph.D.)--University of Colorado at Boulder, 2009.; Dissertation Abstracts International, Volume: 70-04, Section: B, page: 2320.; 374 p.
GaMe3 for Ga2Se3 CVD
Trimethylgallium GaMe3 in combination with hydrogen selenide H2Se or ditertiarybutylselenide SetBu2 was used as precursor for the growth of cubic Ga2Se3 films on nearly lattice matched GaP and mismatched GaAs substrates by MOVPE. Due to pre-reactions of GaMe3 with H2Se only partially epitaxial films were obtained.
In contrast, GaMe3 with SetBu2 produced films of the best crystal quality under steady state flow conditions. GaAs was found to be an unsuitable substrate for MOVPE growth of gallium selenide due to exchange reactions at the interface leading to poorly bonded films.[451, 452, 453]
The mechanism of the reaction of GaMe3 with H2Se was investigated in [[i]]
[i] Nicholas Maung, Guanghan Fan, Tat-Lin Ng, John O. Williams and Andrew C. Wright, J. Mater. Chem., 1999, 9, 2489-2494 , “A study of the mechanism of the reaction of trimethylgallium with hydrogen selenide”
Trimethylgallium triethylphosphine adduct GaMe3·PEt3
GaMe3·PEt3 for InGaAs , InGaAsP MOCVD
The pre-formed trimethylgallium triethylphosphine adduct GaMe3: PEt3 , in combination with InMe3:PEt3, and addition of AsH3 and PH3 as hydride sources, was successfully applied as the precursor for the atmospheric pressure MOVPE growth of GaInAs/InP MQW and CW GaInAsP DH lasers. Threshold currents as low as 53 mA were measured for the RT- CW operated GaInAsP DH lasers; GaInAs/InP MQW lasers operated at RT showed a clear spectral narrowing compared to DH lasers. These results show that GaMe3: PEt3 is good precursor for the MOVPE of Ga-contaning layers like InGaAs and InGaAsP. [[i]]
[i]Nelson, A.W.; Moss, R.H.; Regnault, J.C.; Spurdens, P.C.; Wong, S.; Electronics Letters, Issue Date: April 11 1985, Volume: 21 Issue:8, p.329 - 331 , “Double heterostructure and multiquantum-well lasers at 1.5-1.7 μm grown by atmospheric pressure MOVPE”
Triethylgallium GaEt3
Triethylgallium GaEt3 is the second most popular precursor, as compared to the trimethylgallium, in the growth of Ga-contaning layers by MOCVD/MOVPE.
The important advantage of GaEt3 is that it produces lower carbon contamination due to decomposition by β-hydride elimination rather than by radical mechanism. GaEt3 has lower stability compared to GaMe3 and pyrolyses at significantly lower temperatures (thus allowing to grow higher purity layers at low growth temperatures, compared to trimethylgallium.
For example, when growing InGaN quantum wells (QWs) in the GaN-based LED’s, triethylgallium is usually used because of the low growth temperature of the QWs indispensable for the sufficient indium incorporation in the InGaN layers.
However, the use of GaEt3 is limited due to strong parasitic reactions.
Triethylgallium GaEt3 (M=156.91) is a liquid at room temperature (mp.-82.3°C, bp.143°C, d = 1.06 g/ml), but, compared to trimethylgallium, has lower vapour pressure (log10P(Torr) = 8.08-2062/T(K) ). This however can be considered as an advantage in terms of controlling the molar flow of precursor (e.g., for a typical molar flow of 20 μmol/min, a low (and tricky to control) carrier gas flow of 4.8 sccm is needed for GaMe3 with bubbler temperature 0°C, while with GaEt3 at 20°C a carrier flow of 100sccm (much easier to control) allows to achieve the same molar flow) [3]
Vapor pressure examples at different temperatures: 5.0 Torr@ 20 °C, 39.0Torr@ 60 °C, 90.2 Torr@ 80 °C.
Synthesis
GaEt3 was synthesized for the first time in 1932 [[i]]
Purity
The purity of MOCVD chemicals is significantly higher, compared to earlier times. F.e., in 1990 triethylgallium sample measured by Fourier transform ion cyclotron resonance mass spectrometry (FTICR). was only 53% pure with large amounts of hydrocarbons (46%), ethyl chloride (0.7%), and hydrogen sulfide (0.08%).[573]
[i] Dennis LM, Patnode W, Gallium triethyl etherate, gallium triethyl, gallium triethyl ammine, J. Am.Chem. Soc. 1932; 54: 182-188.
Adsorbtion on the surfaces
Adsorption dynamics of triethylgallium on the GaAs(100) As-rich c(2 × 8) surfaces was studied. (see details Et2GaCl).[432]
Adsorption of GaEt3 as well as NH3 and N2H4 on MgO (100) at 120-160K were studied. Exposure of preadsorbed TEG to NH3 yields a TEG-NH3 adduct; the reverse sequence does not displace NH3 from the surface. However, preadsorbed N2H4 reactsimmediately upon exposure to TEG. [[i]]
The surface chemistry of triethylgallium GaEt3, as well as triethylaluminum AlEt3, triethylindium InEt3, and triethylantimony SbEt3 was studied on GaAs(100) using thermal desorption spectroscopy, static SIMS, and XPS. Ethylene, the major hydrocarbon reaction product, desorbs from the GaAs(100) surface during thermal desorption spectroscopy experiments at 565 K for all four molecules, indicating an identical rate limiting step for the elimination of ethyl groups from the surface following adsorption of these molecules. It was proposed that ethyl groups migrate to Ga sites and then undergo reaction at these sites [[ii]]
[i] V.M. Bermudez, J. Phys. Chem., 1994, 98, 2469-2477
[ii] John M. Heitzinger, M. S. Jackson, and J. G. Ekerdt, Appl. Phys. Lett. 66, 352 (1995); doi:10.1063/1.114210
Decomposition mechanism on solution
In the toluene radical scavenger medium, the decomposition was reported to occur by radical formation with first step (GaEt3 → GaEt2· + Et·) being rate limiting with an activation energy of 47 kcal/mol [[i]]
However, during homogeneous decomposition of GaEt3 (f.e. in atmospheric pressure MOCVD reactor), the pyrolysis occurs via β-hydride elimination mechanism:
1 step) Ga(C2H5)3 → GaH(C2H5)2 + C2H4
2 step) GaH(C2H5)2 → GaH2(C2H5) + C2H4
This was supported by the ethene being the main decompsoition product, and was definitively proven by the absence of ethyl radicals when using matrix isolation techniques with IR LPHP [[ii]]
However, in hot wall low pressure systems, heterogeneous reactions produce ethyl radicals in addition to the main β- elimination decomposition mechanism. Besides ethane decomposition product, butane C4H10 was detected as well, supposedly formed by recombination of ethyl radicals. The temperature dependence of partial pressures of various products suggests that pyrolysis occurs by ethyl radical loss at lower temperatures and predominantly by β-elimination at higher temperatures. [2] Ab initio calculations gave activation energies 59 kcal/mol for radical decomposition mechanism and 44 kcal/mol for β-hydride elimination [380]
Pathways for homogeneous thermal decomposition of GaEt3 were investigated using in situ Raman spectroscopy measurements in an up-flow, cold-wall CVD reactor. The results of Density Functional Theory (DFT) calculations were used to assign measured Raman bands to GaEt3 and decomposition products (GaEt2)2, EtGaH–GaEt2 and EtGaH–GaH2. The results of this study are consistent with both β–hydride elimination and homolysis pathways active (Fig.). [455]
[i] J. Lee, Y. S. Kim, T. Anderson, AIChE Ann. Conf., Nov 2009, Nashville
[ii] W. Ahmed, J.S. Foord, N.K. Singh, R.D. Pilkington, J. de Physique IV, Colloque C2, suppl. au Journal de Physique II, Vol.1, Sept. 1991 , C2-p.193-199
Decomposition mechanism on GaAs
The relative contribution of each mechanism depends on the deposition conditions (Fig.) (precursor concentration and distance from susceptor) [[i]]
Decomposition of GaEt3 on GaAs surface was studied by supersonic moolecular beam system. GaEt3 molecules were bombarding GaAs surface in high vacuum conditions and resulting products were detected by quadrupole mass-spectrometry.(Fig.) [[ii]]
[i] M.C. Paputa, S.J.W.Price, Can. J. Chem, 1979, vol.57, p.3178
[ii] D.K. Russell, Chem. Vap. Deposition, 1996, vol.2, p.223
GaEt3 for GaAs growth by MOCVD
Growth of GaAs layers with GaEt3 results in lower carbon contamination and very high mobility at 77K (as good as 210000 cm2/Vs, among the highest mobilities reported for GaAs grown by any technique). [2]
GaEt3 for GaAsSb growth by MOCVD
GaEt3 for GaAsSb growth by MOCVD
GaEt3 in combination with a variety of group(V) sources (AsH3/ PH3 and As2/P2) was used for fabrication of a GaAsSb solar cells with an active area energy conversion efficiency of 26.7% by Vacuum Chemical Epitaxy (VCE), a method combining advantages of molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). This process utilises multiple group(III)-alkyl molecular beams directed onto wafers, while the group(V) source is injected at a single point on one side of the deposition zone. [[i]]
[i] L. M. Fraas, P. S. Mcleod, L. D. Partain, M. J. Cohen and J. A. Cape, Journal of Electronic Materials, Volume 15, Number 3, 175-180, DOI: 10.1007/BF02655333
Vacuum chemical epitaxy utilizing organometallic sources
GaEt3 for GaN growth by MOCVD
In the case of device grade-quality GaN layers, a slight difference in the optimum growth temperature was observed between GaEt3 as precursor (980-1000°C) vs. GaMe3 producing best layers at higher temperature (1030-1080°C). The difference cannot be explained in terms of different bond strength between gallium atom and the organic radical (Et or Me), since both bonds are pyrolysing below 400°C. [3] Probably it is related to the lower carbon contaminant incorporation at lower temperatures with GaEt3 (easier /cleaner elimination of Et in the form of ethane due to β-elimination decomposition mechanism), while GaMe3 needs higher temperature to reduce carbon contaminants in the form of residual methyl groups (α-elimination decomposition mechanism).
Triethylgallium GaEt3 and ammonia in helium carrier were used for the MOCVD growth of GaN films on Si(100) and Al203(0001) substrates. A two-step deposition process reproducibly producing continuous crystalline GaN films has been developed. SEM, RHEED, AES were used for the study of film microstructure and composition.[464]
The residual strain measured by micro-Raman spectroscopy in the GaN epilayers grown on sapphire from GaEt3 by MOCVD (N2 carrier gas, Tdep 850 °C, reactor pressure of 76 Torr, inlet NH3/Ga molar ratio ~3000) is smaller than in GaN grown from GaMe3by H-MOVPE (Tdep 900 ºC, atmospheric pressure, inlet N/Ga ratio 125, HCl/Ga ratio 2): in GaEt3-MOCVD grown films biaxial strain energy varied from 0 (GaN surface) to 5.0 kJ/mole (GaN/sapphire interface) vs. 6.5 kJ/mole (hydrostatic strain on GaN surface) to 25.0 kJ/mole (biaxial strain on GaN/sapphire interface) for GaMe3-H-MOVPE grown samples. ..[454,463]
GaEt3 for GaP growth by MOVPE
Triethylgallium GaEt3 in combination with phosphine PH3 have been successfully applied for the growth of single crystal GaP epilayers by MOVPE on Si substrates. The optimum growth temperature was 660°C and the optimum molar ratio P / Ga = 13 / 1. The as-grown GaP layer was n-type; the carrier concentration at RT was 3*1016-8.5*1016 cm-3 and mobility 50-100 cm2/Vs. I-V and C-V measurements of this heterojunction device detected leakage current of few tenths of a μA and the breakdown voltage 12 V, a linear CV relationship was obtained. The diode had wide wavelength range of photo-response (from 0.5 μm to 1.2 μm). [461].
GaEt3 for InGaP growth by MOVPE
Triethylgallium GaEt3 was successfully applied for the low-pressure MOVPE growth of highly uniform (σ WL of 1.1 nm) lattice matched InGaP/GaAs heterostructures for short wavelength applications (λ ∼ 650 nm) in a vertical, high speed, rotating disk reactor. Triethylgallium GaEt3 precursors was vaporized at 25°C. Layers were characterized by XRD, SEM, and RT-PL mapping. [[i]]
[i]M. A. McKee, T. McGivney, D. Walker, K. Capuder, P. E. Norris, R. A. Stall, B.C.Rose, J. Electronic Mater., 1992, Vol.21, Num. 3, 289-292, DOI: 10.1007/BF02660456, “ Multi-wafer growth of highly uniform InGaP/GaAs by low pressure MOVPE”
Triisopropylgallium Ga(iPr)3
The pyrolysis temperature of higher gallium alkyls like triisopropylgallium Ga(C3H7)3 (GaiPr3) is significantly lower than for GaEt3. These precursor also pyrolyses by β-hydride elimination mechanism according to earlier IR LPHP studies [2] No evidence of homolytic bond cleavage was found [[i]]
However, more recent study of the same group using matrix isolation technique allowing to trap free radicals, showed that for more carbon atoms containing alkyl ligands the importance of radical decomposition is increasing, while β-elimination becomes less pronounced. Isopropyl radical were reported to be able as well to abstract H from the parent ligand.[[ii]
[i] A.S. Grady, R.E. Linner, R.D. Markwell, G.P. Mills, D.K. Russell, P.J. Williams, A.C. Jones, J. Mater. Chem., 1992, vol.2, p539
[ii] D.K. Russell, G.P. Mills, J.B. Raynor, A.D. Workman, Chem. Vapor Deposition, 1998, vol.4, p.61
Tris(tertiarybutyl)gallium Ga(tBu)3
GatBu3 thermal decomposition
The decomposition of tris (tertiarybutyl)galliumGa(C4H9)3 (GatBu3) was studied in a tubular hot-wall reactor coupled with a molecular-beam sampling mass spectrometer. [[i]] The[PS1] pyrolysis temperature of GatBu3 - is also much lower (260°C) compared to GaMe3 (480°C) and GaEt3. Tris (tertiarybutyl)gallium pyrolyses by β-hydride elimination mechanism as well, producing predominantly i-butane and i-butene as major species (compared to mainly methane (and ethane to a lesser extent) for GaMe3. The predominance of surface reactions was determined; it was found that radical decomposition path of GatBu3, responsible for the formation of butane, is restricted to a narrow temperature range, in contrast to the molecular route that is responsible for the for the formation of the corresponding alkene (2-methylpropene).
[i] Naoufal Bahlawane, Frank Reilmann, Linda-Christin Salameh, and Katharina Kohse-Höinghaus, . (J Am Soc Mass Spectrom 2008, 19, 947–954)
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